As the industry develops, the amount of power generated using fossil fuels increases, and accordingly, environmental problems such as global warming arise. In addition, there is a need for development of new energy sources substituting for the fossil fuels due to the limited fossil fuel reserves. To solve these problems, various power generation methods using water, nuclear energy, solar heat, tidal current, or the like have been proposed and have become commercialized.
Since Korea has the shores having a large tidal range, Korea has a topographical advantage in generating tidal power. In particular, in the western sea and the southern sea of Korea, which have many groups of islands, there are many straits and waterways in which strong tidal currents are generated between islands and land or between islands. Therefore, there is great potential for tidal current power generation using this topographical advantage.
For example, in the case of the Uldolmok strait, known as having the fastest tidal current in Korea, the highest speed of the tidal current when the tide is in and out reaches 5-6 m/sec, which is three times higher than in the normal sea, and thus the Uldolmok strait is evaluated as having the optimum condition for tidal current power generation.
Typical tidal current power generation methods are divided into a method of installing a tower-shaped structure provided with a power generation device therein in the sea, a method of installing a structure having an axial-flow type blade embedded therein in the bottom or middle of the sea, and a method of using a floating body like a ship having a power generation water wheel installed therein.
The tower-shaped structure having the tidal current power generation device embedded therein is disclosed in Korean Patent Registration No. 10-0762375.
To firmly fix the tower-shaped structure to the bottom of the sea, an undersea foundation should be established. However, in a strait having the strong tidal current, there are disadvantages that it is very difficult to establish the undersea foundation and much cost is required. In addition, since the structure is always fixed in the water having the strong tidal current, materials easily break off after being installed, which causes a defect, and it is very difficult to maintain and repair the structure.
The method of installing the structure having the propeller type blade power generation device embedded therein in the bottom or middle of the sea is disclosed in Korean Patent Registration No. 10-1222187 and Korean Patent Publication No. 10-2012-0075251.
These devices have the same problems as the tidal current power generation device installed in the tower-shaped structure in that the structure having a power generation device installed therein should be fixed to the bottom of the sea
The method of using the floating body like a ship having a power generation water wheel installed therein is disclosed in Japanese Patent Publication No. H7-301171 and Korean Patent Registration No. 10-1039080, and a normal configuration of this method is that a water wheel for using water flowing down the floating body or along the side surface of the floating body is installed.
Referring to the related-art methods in detail, the technology disclosed in Japanese Patent Publication No. H7-301171 is installing a water wheel between a pair of boat-shaped hollows having a predetermined gap therebetween, and using the water wheel in a narrow space such as a tailrace of a dam. Since the disclosed structure is usable only on a surface layer of water, it is difficult to apply this method to a relatively deep point of water such as a strait. In addition, since the pair of boat-shaped hollows are simply connected to a connection support, the hollows are likely to be damaged in a harsh environment such as sea.
The technology disclosed in Korean Patent Registration No. 10-1039080 is moving a ship provided with a power generation device to a place where a dike for tidal current power generation will be constructed and then filling the ship with seawater, dropping down the ship to a waterway, and fixing the ship to the bottom. Therefore, there is an advantage that power generation equipment enabling the ship to serve as a dike can be established. However, since this technology enables the ship to serve as a dike, there is a limitation to moving the ship when the ship is fixed in position and generates power, and there is a problem that it is difficult to install a power generation water wheel on the bottom of the ship since the ship is always in contact with water.
In addition, typical related-art tidal current power generation devices including the above-mentioned related-art technologies smoothly generate power when the speed of the tidal current is fast, but there is a problem that efficiency of power generation is abruptly reduced when the speed of the tidal current is slow, for example, at the time of stand of tide. As described above, the related-art tidal current power generation methods have the problems that a uniform amount of power is not generated and efficiency of using tidal current energy is low.